All zigzag sewing machines require a device for imparting motion to the needle transverse to the path of material feed. These devices, sometimes referred to as needle jogging mechanisms, operate in a reciprocating motion, most commonly at a repetition rate of one for every two revolutions of the sewing machine drive shaft.
One mechanism used in zigzag sewing machines is disclosed in U.S. Pat. No. 875,620 by Parkes. This mechanism has a yoke embracing an edge cam. The yoke has two flat surfaces, one being adjustable, for following the edge convolutions of the cam. The adjustable side allows for variations due to wear or manufacture. While this mechanism does provide the reciprocating motions needed by the zigzag control mechanism, at the speeds over which industrial machines are run, wear due to the sliding of the cam edge over the yoke and inertia due to the mass of the yoke assembly, become critical factors which limit the effectiveness of the construction disclosed in this Parkes patent.